This invention relates generally to devices for dispensing or injecting a fluid at a controlled rate and more particularly to a device for use in the medical field to inject fluids into the body of a patient at controlled rate over a prescribed period of time.
It is desirable in the medical profession to inject fluids such as liquid medicaments into the body of the patient, whether human or animal, at a relatively slow rate over a prolonged period of time. Several varieties of medical treatments such as chemotherapy, pre-and post-surgery treatments for the prevention of blood clotting, various nutrient treatments, various antibiotic treatments and treatment of certain other diseases generally require low rates of injection over a long period of time. Such injections are generally made intravenously or subcutaneously into the patient. Some of these treatments generally require that the fluid be introduced relatively continuously over some period of time at some selected rate. Different treatments may require widely varying injection rates. Because of significant increase in the predetermined rate of injection during these continuous treatments must be accurately controlled to prevent serious injury to or fatality of the patient, the rate of injection must be frequently and closely monitored.
There are a number of liquid dispensing or injection devices presently known which attempt to dispense or inject a liquid into a patient at a continuous rate over an extended period of time. These prior art injection systems, however, suffer from a number of drawbacks.
One drawback of such prior art injection systems is that they have tended to be complex in construction and bulky in size. Another drawback of such prior art injection systems is that the injection rate was typically inaccurate and thus required frequent monitoring by trained hospital personnel. Yet another drawback to such systems is that the capital cost thereof is too high for the systems to be disposable. As a result, use of these prior art systems has been limited primarily to hospital settings and under conditions which severely encumber ambulation by the patient. This keeps the utilization costs of such systems high. Moreover, injection rate adjustments had to be made at the site of the patient rather than at the pharmacy where the medication is prepared, thereby increasing the likelihood of error in the delivered dosage rate.